1. Field of the Invention
The present invention relates to a method and apparatus for carrying out abnormality diagnosis of a so-called wide range air-fuel ratio sensor.
2. Description of the Related Art
As a conventional so-called wide range air-fuel ratio sensor, there is for example the devices disclosed in Japanese Unexamined Patent Publication Nos. 1-123141, and 1-124758.
With these devices, a specific constituent concentration (for example oxygen concentration) in the engine exhaust is detected, and based on this, the air-fuel ratio can be detected over a wide range (in both the lean and rich air-fuel ratio regions).
However, technology for diagnosing for example that such a so-called wide range air-fuel ratio sensor is able to operate normally, or that the performance has not deteriorated, has not yet been established. Hence it cannot be known if a wide range air-fuel ratio sensor can correctly detect the air-fuel ratio. There is thus the possibility of a fault for example in the air-fuel ratio control of an internal combustion engine, and hence the possibility that operating performance, exhaust performance, fuel consumption performance and the like cannot be suitably maintained.